You have a flat bolt too!
My bolt is not flush with the mud guard.
The car has been raised 10mm now but it is still hitting that mud guard and more worryingly that bolt.
So this weekend or maybe this week (use the work workshop) I'll take both the rear mudguards off, find the belt sander and sand them down. Probably also put them back on minus one of the bolts.
It rarely rubs with just me in the car but it definently does with 2 or 3 people in it.